A Critical Examination of Li Pollution and Giant-Planet Consumption by a Host Star
A Critical Examination of Li Pollution and Giant-Planet Consumption by a Host Star
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对主恒星锂污染和巨行星消耗的严格检验
DOI：
10.1086/340452
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
R. Mardling
中科院分区：
文献类型：
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作者：
E. Sandquist;J. Dokter;D. Lin;R. Mardling
考虑到在许多有行星的恒星（SWPs）中观察到的高金属含量，我们研究了一颗巨行星的消耗可能污染其宿主星星的总体可能性。首先，我们讨论6Li和7 Li作为污染指标，验证6Li是星星形成后3000万年污染的一个强有力的指标，并表明它强烈地限制了重元素污染纳入星星的数量。SWP中6 Li的检测还可用于区分巨行星形成理论，并可用于检测与行星质量无关的巨行星的消耗。其次，我们研究了1到3兆焦耳的巨行星在质量略大于太阳的恒星的外对流区被摧毁的可能性（对于这种情况，检测污染的化学特征将是最容易的）。我们发现，加热的巨行星在靠近星星表面的地方会被有效地摧毁，而冷的巨行星的核心可能会在穿过星星对流区的底部时幸存下来。第三，我们研究动力学过程是否可以使一颗巨行星足够接近星星以摧毁它，以及一颗行星的毁灭是否必然会影响系统中的其他行星。虽然原行星与其初生盘之间的潮汐相互作用可能使它们接近其宿主恒星，但形成后的恒星-行星相互作用可能导致行星的潮汐破坏和其物质的吸积或轨道衰变，然后是流体动力学相互作用。在整个过程中，我们考虑的情况下HD 82943，一个星星与初步检测6锂，是已知的有两颗行星。使用包括扩散的恒星模型，我们估计HD 82943的质量约为1.2 M，年龄约为0.5-1.5 Gyr。HD 82943的7 Li丰度与疏散星团NGC 752中类似Teff和年龄的恒星一致。我们描述了一个假设的行星在目前已知的两个共振行星的存在下可能的动力学历史。我们提出了稳定的轨道配置，其中假设的行星具有低偏心率和半长轴附近的0.02 Au，使它是动态解耦的共振行星。潮汐与缓慢旋转的星星的相互作用随后会在星星的年龄内将行星拖到恒星表面。
Given the high metal contents observed for many stars with planets (SWPs), we examine the overall likelihood that the consumption of a giant planet could pollute its host star. First, we discuss 6Li and 7Li as indicators of pollution, verifying that 6Li is a strong indicator of pollution 30 Myr after star formation and showing that it strongly constrains the amount of heavy-element pollution incorporated into the star. Detection of 6Li in SWPs could also be used to distinguish between giant planet formation theories and can be used to detect the consumption of giant planets independent of planet mass. Second, we examine the probability that giant planets between 1 and 3 MJ could be destroyed in the outer convection zone of stars slightly more massive than the Sun (for which detection of a chemical signature of pollution would be easiest). We find that heated giant planets would be efficiently destroyed near the surface of the star, while the cores of cold giant planets might be able to survive a plunge through the base of the star's convection zone. Third, we examine whether dynamical processes could bring a giant planet close enough to the star to destroy it and whether the destruction of a planet would necessarily affect other planets in the system. While tidal interaction between protoplanets and their nascent disks may have led them to the proximity of their host stars, postformation star-planet interaction can lead to tidal disruption of the planet and accretion of its material or orbital decay followed by hydrodynamical interaction. Throughout, we consider the case of HD 82943, a star with a preliminary detection of 6Li that is known to have two planets. Using stellar models including diffusion, we estimate the mass of HD 82943 to be ~1.2 M☉ and its age to be ~0.5-1.5 Gyr. The observed 7Li abundance for HD 82943 is consistent with stars of similar Teff and age in the open cluster NGC 752. We describe a possible dynamical history for a hypothetical planet in the presence of the two resonant planets currently known. We present stable orbital configurations in which the hypothetical planet has low eccentricity and semimajor axis near 0.02 AU, so that it is dynamically decoupled from the resonant planets. Tidal interactions with the slowly rotating star can subsequently drag the planet into the stellar surface within the age of the star.